1. Technical Field
The present invention relates to a polymeric phase-change material preparation technology, and more particularly to a preparation method of a polymeric phase-change material with heat storage and release functions.
2. Related Art
Phase-change materials are a type of energy-saving and environmental-friendly materials that are developed and applied in 1970s. During phase change, the phase-change material can absorb or release a great amount of latent heat, are widely used in the fields of heating, ventilating and air conditioning, construction, use of solar energy, and clothing, and have great significance in the aspect of “energy saving and emission reduction”. The most widely used phase-change materials are classified into the following two types, namely, solid-liquid phase-change materials such as normal paraffins, and hydrated inorganic salts and solid-solid phase-change materials such as polyols. Most of the solid-liquid phase-change materials are low-molecular-weight compounds, such as inorganic salts, normal paraffins, high fatty alcohols, high fatty acids or high fatty esters. When phase change occurs, the volume change is large, and the thermal stability of the normal paraffins and the hydrated inorganic salts is poor. When being in a liquid state, the materials easily flows, so that the shape retention property is poor, and loss or pollution are likely caused. Due to the phase change, the materials need to be sealed in a container or to be mixed with other absorption support material to obtain a fixed shape before use. As for the solid-solid phase-change materials such as high fatty alcohol, high fatty acid or high fatty ester phase-change materials, when being heated to a temperature higher than the solid-solid phase change temperature, the materials are changed from a crystalline solid into a plastic crystal, because the vapor pressure is high, the materials are easily volatilized and suffers loss, so that the materials needs to be sealed in a container in use. Moreover, as the phase change temperature is high, it is difficult for the phase change materials to satisfy the requirements for use in a low-temperature environment. In addition, there are few types of such materials, therefore few choices are available in the industry. The currently known polymeric phase-change materials are mainly aliphatic polyether and aliphatic polyester, such as polyethylene glycol, polybutylene glycol and polyhexamethylene adipate. However, as the materials are solid-liquid phase-change materials, and when being in a molten state, the materials easily flows; moreover, the heat-resistant temperature is low, the use is also limited. Chinese Invention Patent CN1616588A discloses a preparation method of a high-molecular weight phase-change material. According to the structure of the material, an organic material having a low melting point and high phase change enthalpy are fixed on a high-melting point or infusible framework through a chemical bond, which is specifically fixing a polymeric phase-change material polyethylene glycol having two active terminal groups and a polyethylene glycol having one active end group on a high-molecular weight framework material, to form a three-dimensional network and comb composite structure, so that the material maintains the solid state during phase change, and has the solid-solid phase change characteristics. Chinese Invention Patent CN1710012A discloses a technology of preparing a solid-solid phase-change material by grafting polymeric phase-change material having an active group at one terminal or two terminals, namely, polyethylene glycol on a surface of nano-cellulose or a derivative thereof. In the two invention patent applications, polyethylene glycol is used as the phase-change material, so the application scope is narrow. In an earlier patent, namely, Chinese Invention Patent CN101798364A, the applicant of the present invention discloses a preparation method of a novel polymeric phase-change material poly(n-alkyl methacrylate), where solid-solid phase change of the phase-change material is achieved without using a framework material. However, due to the existence of the ester group with strong polarity in the polymeric phase-change material, a part of carbon atoms in the n-alkyl cannot be crystallized; moreover, the phase change enthalpy is low.